1. Field of the Invention
The present invention relates to a novel one pot process for the preparation of an .alpha.-aryloxy acetic acid having the general formula EQU RO--CH.sub.2 COOH
or a salt thereof, wherein R can be aryl which can optionally be substituted by one or more substituents selected from the group consisting of straight or branched chain alkyl, alkoxy, alkoxy alkyl, halo, phenyl, substituted phenyl, hydroxy, and 2-methylene-1-oxobutyl; which comprises reacting an alcohol of the formula EQU R--OH
wherein R is defined as above, with a suitable base in an aprotic organic solvent to generate an aryloxide anion, removal of the organic solvent, and coupling of the aryloxide anion with a salt of a monohaloacetic acid in an aprotic polar solvent such as dimethyl sulfoxide (DMSO) to give the aryloxy acid salt which can be recovered or can optionally be reacted with acid to give the .alpha.-aryloxy acetic acid product. This process has the advantages of providing a high yield of product and being able to be conducted in one pot thus providing a quicker, more efficient and less costly synthesis. The process of the present invention permits the unexpectedly efficient and convenient preparation of .alpha.-aryloxy acetic acids in improved overall yield and purity.
(b) Prior Art
U.S. Pat. Nos. 4,711,903 and 4,755,524 disclose a method of preparing a [2-[[3,5 bis(1,1-dimethylethyl) 4-hydroxyphenyl]thio]-alkoxy]acetic acid from a 2,6-bis (1,1-dimethylethyl) 4-[(2 hydroxyalkyl) thio]phenol by a process in which chloroacetic acid is added to the alcohol in t-butyl alcohol which is a protic solvent, then potassium tert-butoxide is added, and the mixture is refluxed. This method gives yields of less than 25% and thus is not a very efficient process.
U.S. Pat. No. 4,804,777 discloses a process for the preparation of an aryloxy acetic acid by oxidation of an aryloxyethanol in an aqueous alkaline reaction medium at a temperature in the range of 0.degree. C. to the boiling point of the reaction medium in the presence of a catalytic amount of a catalyst comprised of palladium, silver, and optionally antimony, and carbon to form the corresponding alkali metal ester and contacting the alkali metal with a mineral acid.
U.S. Pat. No. 3,918,899 discloses a method of preparing carboxymethylated cottons in non-aqueous media by reacting anhydrous sodium cellulosate with a salt of a monochloroacetate in an anhydrous DMSO solution.
R. C. Fuson and B. H. Wojcik, ORGANIC SYNTHESIS COLLECTED VOLUMES, 2:260-262(1943) discloses a three-step method for preparing ethoxyacetic acid from ethanol which is the substrate and the solvent (protic solvent).